1. Field of the Invention
The present invention generally relates to a digital display apparatus capable of supporting an error compensation and a method thereof, and more specifically, to a digital display apparatus to compensate an error by converting a working state of a signal amplifier when an error is detected in a digital signal, and a method of the same.
2. Description of the Related Art
According to the development of electronic technology, a broadcasting system has been changing from analog to digital. A digital broadcasting system may be defined as a TV broadcasting system that processes broadcasting steps such as producing, editing, transmitting, and receiving, by the digital signals of 0 and 1. Usually, the digital broadcasting system is compared with an analog broadcasting system which processes and encodes data with a different voltage according to a type of the data such as video, audio, and teletext.
With the analog system, brightness of a light or volume of a sound is encoded with voltage. Hence, there is a shortcoming that a noise or a reflection may occur during the signal transmission so that a video of a high definition may not be outputted.
To overcome the above shortcoming, a digital signal processing technology has been introduced for the broadcasting system. The digital signal processing refers to a series of processes in which a video data and an audio data are respectively compressed, encoded to numbers for the transmission, multiplexed, and transmitted as the single digital data stream. In addition, a receiver receives the data, debugs an error, demultiplexes and decodes the data into the video and the audio.
For example, when a sender transmits a number 1, a receiver receives a signal having the number 1, although a noise may be added to the signal or the signal may be reflected by an obstacle during the transmission. Hence, transmitted information can be reproduced as it is.
In the digital broadcasting system, there is a digital display apparatus which receives the video and the audio signals transmitted as the digital signals and outputs them on a screen, specifically a digital television (TV) such as a high definition (HD) TV or a standard definition (SD) TV.
The HD-TV uses 1080 vertical scanning (interlaced scanning) lines and 1920 horizontal scanning lines and supports an aspect ratio of 16:9 and a Dolby digital surround audio. The SD-TV uses a frequency bandwidth less than the HD-TV and displays with a resolution of 720×480 for supporting services such as data broadcasting, simulcasting and VOD (Video on Demand).
FIG. 1 is a block diagram showing a general construction of the digital display apparatus used for the digital broadcasting system, specifically for the digital TV.
Referring to FIG. 1, an antenna 10 receives a digital signal transmitted from a broadcasting station and a signal amplifier 20 amplifies the received digital signal. As the digital signal is weakened during the transmission from the broadcasting station to the intended antenna, the input signal is required to be amplified for subsequent processes. Generally, in the TV, a low noise amplifier (LNA) is used to amplify the weakened signal to the interpretable signal and remove the noise which is added during the transmission.
The signal amplified by the signal amplifier 20 is demodulated by a signal demodulator 30 and outputted as the video and audio data streams.
The broadcasting station modulates the digital signal through a modulation method such as ASK (amplitude shift keying), FSK (frequency shift keying), PSK (phase shift keying), OFDM (orthogonal frequency division multiplex), and TCM (trellis coded modulation). Accordingly, the receiver, i.e., the digital TV has to demodulate the modulated digital signal and recover the original signal from the modulated signal.
For the demodulation of the digital signal, a synchronous detection system or a delay detection system may be used. The synchronous detection method performs the demodulation by extracting a carrier from the received signal and adding the carrier and the received signal. The delay detection method adds the received signal which is delayed by 1 symbol and demodulates with a phase difference between the symbols.
The signal demodulated by the signal demodulator 30 is converted to the signal for the output in a digital signal process unit 50 by the control of a control unit 40 and outputted on the screen. Meanwhile, an external device 60 connected to the digital TV is inputted with an amplified signal looped out from the signal amplifier 20. As the external device 60, there may be a DVD player, a VCR, or a set-top box.
As described above, since the input signal received from the antenna is always amplified by the signal amplifier 20, if a strong signal is amplified and a signal outputted through the loop out is used by the external device 60, a saturation phenomena may arise. In addition, in tuning on/off the TV or changing a channel, if the input signal is abruptly changed, an error bit may be generated during the demodulation of the received digital signal so that a video on the screen may be distorted, frozen, or broken.